Water treatment polymers and methods of use thereof

ABSTRACT

A water soluble polymer composition is disclosed. The polymer has repeat units characterized by the structural formulae: ##STR1## wherein R 1  is H or lower alkyl (C 1  --C 3 ); R 2  OH, OM, or NH 2  ; M is a water soluble cation; R 3  is a hydroxy substituted alkyl or alkylene radical having from 1 to about 6 carbon atoms or a non-substituted alkyl or alkylene radical having from 1 to 6 carbon atoms; X is an anionic radical; Z is H or hydrogens or a water soluble cation or cations which together counterbalance the valence of X, and a is 0 or 1. The copolymer is effective in inhibiting the precipitation of certain scale forming salts, and also acts to inhibit corrosion of metal parts in contact with water systems.

This is a continuation-in-part of application Ser. No. 037,484 filedApr. 13, 1987 (now U.S. Pat. No. 4,759,851), which is a continuation ofSer. No. 864,049 filed May 16, 1986 (now U.S. 4,659,481), which in turnis a continuation of Ser. No. 545,563 filed Oct. 26, 1983 (nowabandoned).

FIELD OF THE INVENTION

The present invention pertains to a composition and method ofutilization of same to inhibit corrosion and control the formation anddeposition of scale imparting compounds in water systems such ascooling, boiler and gas scrubbing systems.

BACKGROUND OF THE INVENTION

The problems of corrosion and scale formation and attendant effects havetroubled water systems for years. For instance, scale tends toaccumulate on internal walls of various water systems, such as boilerand cooling systems, and thereby materially lessens the operationalefficiency of the system.

Deposits in lines, heat exchange equipment, etc., may originate fromseveral causes. For example, precipitation of calcium carbonate, calciumsulfate and calcium phosphate in the water system leads to anaccumulation of these scale imparting compounds along or around themetal surfaces which contact the flowing water circulating through thesystem. In this manner, heat transfer functions of the particular systemare severely impeded.

Corrosion, on the other hand, is a degradative electro-chemical reactionof a metal with its environment. Simply stated, it is the reversion ofrefined metals to their natural state. For example, iron ore is ironoxide. Iron oxide is refined into steel. When the steel corrodes, itforms iron oxide which, if unattended, may result in failure ordestruction of the metal, causing the particular water system to be shutdown until the necessary repairs can be made.

Typically, in cooling water systems, the formation of calcium sulfate,calcium phosphate and calcium carbonate, among others, has provendeleterious to the overall efficiency of the cooling water system.Recently, due to the popularity of cooling treatments using high levelsof orthophosphate to promote passivation of the metal surfaces incontact with the system water, it has become critically important tocontrol calcium phosphate crystallization so that relatively high levelsof orthophosphate may be maintained in the system to achieve the desiredpassivation without resulting in fouling or impeded heat transferfunctions which would normally be caused by calcium phosphatedeposition.

Although steam generating systems are somewhat different from coolingwater systems, they share a common problem in regard to depositformation.

As detailed in the Betz Handbook of Industrial Water Conditioning, 8thEdition, 1980, Betz Laboratories, Inc., Trevose, PA Pages 85-96, theformation of scale and sludge deposits on boiler heating surfaces is aserious problem encountered in steam generation. Although currentindustrial steam producing systems make use of sophisticated externaltreatments of the boiler feedwater, e.g., coagulation, filtration,softening of water prior to its feed into the boiler system, theseoperations are only moderately effective. In all cases, externaltreatment does not in itself provide adequate treatment since muds,sludge, silts and hardness-imparting ions escape the treatment, andeventually are introduced into the steam generating system.

In addition to the problems caused by mud, sludge or silts, the industryhas also had to contend with boiler scale. Although external treatmentis utilized specifically in an attempt to remove calcium and magnesiumfrom the feedwater, scale formation due to residual hardness, i.e.,calcium and magnesium salts, is always experienced. Accordingly,internal treatment, i.e., treatment of the water fed to the system, isnecessary to prevent, reduce and/or retard formation of the scaleimparting compounds and their resultant deposition. The carbonates ofmagnesium and calcium are not the only problem compounds as regardsscale, but also waters having high contents of phosphate, sulfate andsilicate ions either occurring naturally or added for other purposescause problems since calcium and magnesium, and any iron or copperpresent, react with each and deposit as boiler scale. As is obvious, thedeposition of scale on the structural parts of a steam generating systemcauses poorer circulation and lower heat transfer capacity, resultingaccordingly in an overall loss in efficiency.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, it has been surprisingly discoveredthat water soluble copolymers, as shown in Formula I hereinafter, areeffective in controlling the formation of mineral deposits and ininhibiting corrosion in various water systems.

The water soluble copolymers of the invention have the structure:##STR2## wherein R₁ is H or lower alkyl (C₁ -C₃); R₂ is OH or OM, or NH₂; M is a water soluble cation; R₃ is a hydroxy substituted alkyl oralkylene radical having from 1 to 6 carbon atoms or a non-substitutedalkyl or alkylene radical having from 1 to about 6 carbon atoms; X, whenpresent, is an anionic radical selected from the group consisting ofSO₃, PO₃, PO₄, and COO; Z, when present, is H or hydrogens or any watersoluble cation or cations which together counterbalance the valence ofthe anionic radical; a is 0 or 1.

The number average molecular weight of the water soluble copolymers ofFORMULA I is not particularly significant so long as the polymer iswater soluble. The molecular weight may fall within the range of 1,000to 1,000,000, and more likely the number average molecular weight willbe within the range of from about 1,500 to 500,000, with the range ofabout 1,500 to about 20,000 being even more highly desirable. The keycriterion is that the polymer be water soluble.

The molar ratio x:y of the monomers of FORMULA I may fall within therange of between about 30:1 to 1:20, with the x:y molar ratio range offrom about 10:1 to 1:5 being preferred.

At present, the water soluble polymer preferred for use in cooling watersystems is: ##STR3## wherein M is the same as given in FORMULA I. Thispolymer (FORMULA II) is referred to as acrylic acid/allyl hydroxy propylsulfonate ether (AA/AHPSE). The IUPAC nomenclature for AHPSE is1-propane sulfonic acid, 2-hydroxy-3-(2-propenyl oxy)-mono sodium salt.Heretofore, the AHPSE monomer has been used in the emulsionpolymerization of acrylate esters, vinyl acetate and styrene for themanufacture of latex paints. However, to my knowledge, my inventioninvolves the first time this monomer has been polymerized into a watersoluble polymer under aqueous solution polymerization techniques.

With respect to both repeat units of the polymers of the presentinvention, they may exist in acid or water soluble salt form when usedin the desired water system.

As to preparation of the monomer designated as x above, in FORMULA I,acrylic acid is well known. It may be produced by hydrolysis ofacrylonitrile or via oxidation of acrolein. Other well known vinylcontaining monomers such as methacrylic acid and acrylamide may also beutilized as monomer x of FORMULA I in accordance with the invention.

Turning to the allyl containing monomer, monomer y, in the FORMULA Iabove, these may be produced by reacting allyl alcohol with anon-tertiary alcohol in the temperature range of about 25°-150° C. as isdetailed in U.S. Pat. No. 2,847,477 (the entire disclosure of which ishereby incorporated by reference) followed by, if desired, sulfonation,phosphorylation, phosphonation or carboxylation of the monomer viawell-known techniques.

The preferred allyl hydroxy propyl sulfonate ether monomers (monomer yFORMULA II) may conveniently be prepared via a ring opening reaction ofthe epoxy group of an allyl glycidyl ether precursor. Sulfonation of theepoxy group with sodium sulfite in the presence of a phase transfercatalyst such as tetra-n-butylammonium bisulfite or with fuming sulfuricacid containing sulfur trioxide will produce the sulfonic acid group andhydroxy group of the AHPSE. The resulting monomer can be furtherneutralized with caustic or other basic material. The reaction isillustrated by the following mechanism: ##STR4##

Similar ring opening reactions can be carried out by using phosphorousacid and its derivatives including phosphorous trichloride to obtain thephosphonic acid substituents.

If orthophosphoric acid (H₃ PO₄) and its derivatives are used in thering opening reaction, phosphoric acid ester substituents may be formedin accordance with the mechanism: ##STR5##

Such reaction is described in U.S. Pat. No. 2,723,971.

Carboxylate functions can be provided on the allyl hydroxy propyl ethermonomer via the reaction of allyl alcohol and chloro-β hydroxy butanoicacid according to the mechanism: ##STR6##

It should be noted that the monomer y (FORMULA I) may itself be allylglycidyl ether which is commercially available from several sources.

Z in the allyl monomer, (monomer y of FORMULA I) if present, may behydrogen, hydrogens or any soluble cation or cations which togethercounterbalance the valence of the anionic moiety X. Suitable cationsinclude Na, NH₄ ⁺, Ca, and K. X, when present, may be chosen from thegroup consisting of SO₃, PO₃, PO₄, and COO.

After the desired monomers have been obtained, free radical chainaddition polymerization may proceed in accordance with conventionalsolution polymerization techniques. Polymerization initiators such aspersulfate initiators, peroxide initiators, etc. may be used. Preferablythe requisite monomers are mixed with water and alcohol (preferablyisopropanol). The resulting polymer may be isolated by well-knownmethods such as distillation, etc. or the polymer may simply be used inits aqueous solution.

It should be mentioned that water soluble terpolymers comprisingmonomers x and y of FORMULA I or II may also be prepared for use asdeposit control agents and/or corrosion control agents. For instance,AHPSE monomers may be incorporated into a water soluble terpolymerbackbone having other repeat units including acrylic acid monomers,alkyl acrylate monomers, methacrylic acid monomers, acrylamide monomers,etc.

The polymers should be added to the aqueous system, for which corrosioninhibiting, and/or deposit control activity is desired, in an amounteffective for the purpose. This amount will vary depending upon theparticular system for which treatment is desired and will be influencedby factors such as, the area subject to corrosion, pH, temperature,water quantity and the respective concentrations in the water of thepotential scale and deposit forming species. For the most part, thepolymers will be effective when used at levels of about 0.1-500 partsper million parts of water, and preferably from about 1.0 to 100 partsper million of water contained in the aqueous system to be treated. Thepolymers may be added directly into the desired water system in a fixedquantity and in the state of an aqueous solution, continuously orintermittently.

The polymers of the present invention are not limited to use in anyspecific category of water system. For instance, in addition to boilerand cooling water systems, the polymers may also be effectively utilizedin scrubber systems and the like wherein corrosion and/or the formationand deposition of scale forming salts is a problem. Other possibleenvironments in which the inventive polymers may be used include heatdistribution type sea water desalting apparatus and dust collectionsystems in iron and steel manufacturing industries and as a dispersantin the pulp and paper processing industries. Also the polymers could beused as mineral beneficiation aids such as in iron ore, phosphate, andpotash recovery.

The water soluble polymers of the present invention can also be usedwith topping agent components in order to enhance the corrosioninhibition and scale controlling properties thereof. For instance thepolymers may be used in combination with one or more kinds of compoundsselected from the group consisting of inorganic phosphoric acids,phosphonic acid salts, organic phosphoric acid esters, and polyvalentmetal salts. Such topping agents may be added to the system in an amountof from about 1 to 500 ppm.

Examples of such inorganic phosphoric acids include condensed phosphoricacids and water soluble salts thereof. The phosphoric acids include anorthophosphoric acid, a primary phosphoric acid and a secondaryphosphoric acid. Inorganic condensed phosphoric acids includepolyphosphoric acids such as pyrophosphoric acid, tripolyphosphoric acidand the like, metaphosphoric acids such as trimetaphosphoric acid, andtetrametaphosphoric acid.

As to the other phosphonic acid derivatives which are to be added inaddition to the polymers of the present invention, there may bementioned aminopolyphosphonic acids such as aminotrimethylene phosphonicacid, ethylene diaminetetramethylene phosphonic acid and the like,methylene diphosphonic acid, hydroxyethylidene diphosphonic acid,2-phosphonobutane 1,2,4, tricarboxylic acid, etc.

Exemplary organic phosphoric acid esters which may be combined with thepolymers of the present invention include phosphoric acid esters ofalkyl alcohols such as methyl phosphoric acid ester, ethyl phosphoricacid ester, etc., phosphoric acid esters or methyl cellosolve and ethylcellosolve, and phosphoric acid esters of polyoxyalkylated polyhydroxycompounds obtained by adding ethylene oxide to polyhydroxy compoundssuch as glycerol, mannitol, sorbitol, etc. Other suitable organicphosphoric esters are the phosphoric acid esters of amino alcohols suchas mono, di, and tri-ethanol amines.

Inorganic phosphoric acid, phosphonic acid, and organic phosphoric acidesters may be salts, preferably salts of alkali metal, ammonia, amineand so forth.

Exemplary polyvalent metal salts which may be combined with the watersoluble polymers of the invention include those capable of dissociatingpolyvalent metal cations in water such as Zn⁺⁺, Ni⁺⁺, etc., whichinclude zinc chloride, zinc sulfate, nickel sulfate, nickel chloride andso forth.

The water soluble polymers of the present invention may also be used inconjunction with water soluble chromate compounds that are adapted toprovide chromate radicals in water solutions. Illustrative water solublechromate compounds include sodium chromate dihydrate, sodium chromateanhydrous, sodium chromate tetrahydrate, sodium chromate hexahydrate,sodium chromate decahydrate, potassium dichromate, potassium chromate,ammonium dichromate and chromic acid.

In addition, water soluble azole compounds can be used in combinationwith the water soluble polymers herein disclosed. Such azoles have theformula ##STR7## Included within the scope of the invention are N-alkylsubstituted 1,2,3-triazole, or a substituted water soluble1,2,3-triazole where substitution occurs at the 4 and/or 5 position ofthe ring. The preferred 1,2,3-triazole is 1,2,3-tolyltriazole of theformula ##STR8## Other exemplary 1,2,3-triazoles include benzotriazole,4-phenol-1,2,3-triazole, 4-methyl-1,2,3-triazole,4-ethyl-1,2,3-triazole, 5-methyl-1,2,3-triazole, 5-ethyl-1,2,3-triazole,5-propyl-1,2,3-triazole, and 5-butyl-1,2,3-triazole. Alkali metal orammonium salts of these compounds may be used.

Other azole compounds include thiazole compounds of the formula:##STR9##

Suitable thiazoles include thiazole, 2-mercaptothiazole,2-mercaptobenzothiazole, benzothiazole and the like.

The water soluble polymers may also be used in conjunction withmolybdates such as, inter alia, sodium molybdate, potassium molybdate,lithium molybdate, ammonium molybdate, etc.

When the water soluble polymer of the invention (FORMULA I) is added tothe aqueous system in combination with a topping agent componentselected from the group consisting of inorganic phosphoric acids,phosphonic acids, organic phosphoric acids esters, their water-solublesalts (all being referred to hereinafter as phosphoric compounds),polyvalent metal salts, chromates, molybdates, and azoles, a fixedquantity of said polymer may be added separately and in the state ofaqueous solution into the system. The water soluble polymers may beadded either continuously or intermittently. Alternatively, the polymermay be blended with the above noted topping agent compounds and thenadded in the state of aqueous solution into the water system eithercontinuously or intermittently. The topping agents are utilized in theusual manner for corrosion and scale preventing purposes. For instance,the phosphoric compounds or polyvalent metal salts may be added to awater system continuously or intermittently to maintain their necessaryconcentration.

Generally, the phosphoric compounds should be present in the aqueoussystem in an amount of about 1-100 ppm (as PO₄) or the polyvalent metalsalts should be present in an amount of about 1 to 50 ppm (as metalcation).

As is conventional in the art, the phosphoric compounds or polyvalentmetal salts may be added, as pretreatment dosages, to the water systemin an amount of about 20 to about 500 ppm, and thereafter a smallquantity of chemicals may be added, as maintenance dosages.

The polymers may be used in combination with yet other topping agentsincluding corrosion inhibitors for iron, steel, copper, copper alloys orother metals, conventional scale and contamination inhibitors, metal ionsequestering agents, and other conventional water treating agents. Othercorrosion inhibitors comprise tungstate, nitrites, borates, silicates,oxycarboxylic acids, amino acids, catechols, aliphatic amino surfaceactive agents, benzotriazole, and mercaptobenzothiazole. Other scale andcontamination inhibitors include lignin derivatives, tannic acids,starch, polyacrylic soda, polyacrylic amide, etc. Metal ion sequesteringagents include polyamines, such as ethylene diamine, diethylene triamineand the like and polyamino carboxylic acids, such as nitrilo triaceticacid, ethylene diamine tetraacetic acid, and diethylene triaminepentaacetic acid.

EXAMPLES

The invention will now be further described with reference to a numberof specific examples which are to be regarded solely as illustrative,and not as restricting the scope of the invention.

Example 1 Preparation of Acrylic Acid/Allyl Hydroxylpropyl SulfonateEther Copolymer

A suitable reaction flask was equipped with a mechanical agitator, athermometer, a reflux condenser, a nitrogen inlet and two additioninlets for the initiator and monomer solutions. The flask was chargedwith 200 g of deionized water and 26 g of isopropanol. The resultingsolution was then heated to reflux under a nitrogen blanket. 72 g ofacrylic acid (1 mole) and 136 g of 1-propane sulfonic acid,2-hydroxy-3-(2-propenyl oxy) mono sodium salt [AHPSE] (40%, 0.25 mole)were mixed in a separate flask so as to provide a mixed monomersolution. The mixed monomer solution was then transferred to anadditional funnel. An initiator solution containing 27.3% of sodiumpersulfate in deionized water was prepared separately and sparged withnitrogen. The initiator solution (20 ml) was then added to the reactionflask along with the mixed monomer solution over a period of 2 hours.After this addition, the resulting mixture was heated for 2 more hoursat 85° C. and subsequently, 66.5 g of the isopropanol/water solution wasstripped off. The reaction mixture was then cooled to less than 40° C.and 60 g of 50% caustic solution was then added.

The structure of the resulting copolymer was verified by Carbon 13 NMR.The polymer solution, after being diluted to 25% solids with water, hada Brookfield viscosity of 14.5 cps at 25° C. It was a stable solutionwith a slightly yellow color.

Example 2

Utilizing both apparatus and procedure similar to that described inExample 1, 200 g of deionized water and 13 g of isopropanol were changedto a reaction flask. The solution was then heated to reflux temperatureunder a nitrogen blanket. 72 g of acrylic acid and 136 g of AHPSE (40%)were added to a separate flask so as to provide a mixed monomersolution. The mixed monomer solution was then added to the reactionflask along with an initiator solution comprising sodium persulfate overa 2 hour period. The reaction mixture was heated for 2 more hours andsubsequently, 36.4 g of isopropanol/water solution was stripped off. Themixture was cooled to lower than 40° C. and 60 g of 50% caustic solutionwas added.

The resulting polymer solution, after being diluted to 25% with water,had a Brookfield viscosity of 19.8 cps (at 25° C.).

Example 3

Utilizing both apparatus and procedure similar to that described inExample 1, 15 g of isopropanol and 228 g of water were added to areaction flask. 72 g of acrylic acid (1 mole) and 180 g of AHPSE (40%solution, 0.33 mole) were added to an addition funnel so as to provide amixed monomer solution. The mixed monomer solution was then added to thereaction flask along with a sodium persulfate containing initiatorsolution over a 2 hour period. One hour after this addition, a solutionof t-butyl hydroperoxide (0.2 g in 10 ml of water) was added to thereaction mixture. The mixture was heated for 1 more hour andsubsequently, 39.4 g of isopropanol/water solution was stripped off. Themixture was cooled to lower than 40° C. and 60 g of 50% caustic wasadded.

The resulting copolymer solution, after being diluted to 25% solids, hada Brookfield viscosity of 15.9 cps at 25° C.

Example 4

Utilizing the apparatus and procedure described in Example 1, 72 g ofacrylic acid (1 mole) and 90.8 g of AHPSE (40%, 0.167 mole) were usedfor copolymerization. The resulting polymer solution, after beingdiluted to 25%, had a Brookfield viscosity of 14.5 cps (at 25° C.). Thestructure of the copolymer was verified by Carbon 13 NMR.

Example 5

Utilizing the apparatus and procedure as described in Example 1, 72 g ofacrylic acid (1 mole) and 68.1 g of AHPSE (40%, 0.125 mole) were usedfor copolymerization. The resulting polymer solution, after beingdiluted to 25% had a Brookfield viscosity of 15.1 cps (at 25° C.).

Example 6

Apparatus, procedure and reagent charge similar to that described inExample 3 were used, except that this time, AHPSE (180 g, 40% solution)was initially charged into a reaction flask along with isopropanol andwater. Acrylic acid (72 g) and sodium persulfate solution were thenadded to the reaction flask over a 2 hour period. The resultingcopolymer solution, after isopropanol distillation, caustic addition andwater dilution (to 25% solids) had a Brookfield viscosity of 22.5 cps at25° C.

Example 7

Apparatus, procedure and reagent charge similar to that described inExample 4 were used except that this time AHPSE (90.8 g, 40% solution)was charged initially into the reaction flask along with isopropanol andwater. Acrylic acid (72 g) and sodium persulfate solution were thenadded to the reaction mixture over a 2 hour period. The resultingcopolymer solution, after isopropanol distillation, caustic addition,and water dilution, (to 25% solids) had a Brookfield viscosity of 15.4cps (at 25° C).

Table I hereinbelow presents a summary of the physical properties of thecopolymers produced in accordance with Examples 1 through 6.

                  TABLE I                                                         ______________________________________                                                             Viscosity                                                                     (Brookfield                                              Example  AA/AHPSE    25% Soln.                                                Number   Molar Ratio 25° C.)                                                                           Mn     pH                                     ______________________________________                                        1        4:1         14.5       2,550  5.9                                    2        4:1         19.8       3,600  5.5                                    3        3:1         15.9       2,900  5.7                                    4        6:1         14.5       2,080  6.1                                    5        8:1         15.1       2,260  6.7                                    6        3:1         22.5       3,760  6.1                                    7        6:1         15.4       2,217  6.2                                    ______________________________________                                         AA = acrylic acid                                                             AHPSE = allyl hydroxypropyl sulfonate ether; IUPAC 1propane sulfonic acid     2hydroxy-3-(2-propenyl oxy)mono sodium salt.                             

Deposit Control Activity

One method of evaluating deposit control activity of a material consistsof measuring its ability to prevent bulk phase precipitation of a saltat conditions for which the salt would normally precipitate. It isadditionally important to recognize that the material being evaluated istested at "substoichiometric" concentrations. That is, typical molarratios of precipitating cation to the material being evaluated are onthe order of 20:1 and much greater. Consequently, stoichiometricsequestration is not the route through which bulk phase precipitation isprevented. This well known phenomenon is also called "threshold"treatment and is widely practiced in water treatment technology for theprevention of scale (salt) deposits from forming on various surfaces. Inthe results that follow calcium phosphate, calcium carbonate, andcalcium sulfate salts commonly found in industrial water systems undervarious conditions have been selected as precipitants. The polymers ofthe present invention has been evaluated for their ability to preventprecipitation (i.e., inhibit crystallization) of these salts. Zinchydroxide and calcium phosphonate precipitation studies were alsoundertaken as these particular deposit forming species are also commonlyencountered as a result of the use of zinc based corrosion preventiontreatments and phosphonate containing deposit control treatments. Theresults are expressed as "percent inhibition", positive values indicatethat the stated percentage of precipitate was prevented from beingformed. Except as where noted to the contrary, the following conditions,solutions, and testing procedure were utilized to perform the inhibitiontests, the results of which are reported herein in Tables II to VIII.

CALCIUM CARBONATE INHIBITION

    ______________________________________                                        CALCIUM CARBONATE INHIBITION                                                   Conditions     Solutions                                                     ______________________________________                                        pH = 9.0, 8.5   3.25g CaCl.sub.2.2H.sub. 2 O/liter DI H.sub.2 O               T = 70° C.                                                                             2.48g Na.sub.2 CO.sub.3 /liter DI H.sub.2 O2O                 5 hour equilibrium                                                            105 ppm Ca.sup.+2 as CaCO.sub.3                                               702 ppm CO.sub.3.sup. -2                                                      ______________________________________                                    

Procedure

(1) Add 50 ml CaCl₂ ·2H₂ O pre-adjusted to pH 9.0.

(2) Add 40 ml of Na₂ HPO4 solution.

(3) Add 50 ml Na₂ CO₃ pre-adjusted to pH 9.0.

(4) Heat 5 hours at 70° C. water bath. Remove and cool to roomtemperature.

(5) Filter 5 mls through 0.2 u filters.

(6) Adjust samples to pH 1.0 with conc. HCl (≈1 g Conc. HCl).

(7) Allow to stand at least 15 minutes.

(8) Dilute to 50 mls with DI H₂ O.

(9) Bring pH to 12.0 with NaOH.

(10) Add Ca⁺² indicator (1 level).

(11) Titrate with EDTA to purple-violet endpoint.

Calculation: ##EQU1##

CALCIUM PHOSPHATE INHIBITION PROCEDURE

    ______________________________________                                        CALCIUM PHOSPHATE INHIBITION PROCEDURE                                        Conditions       Solutions                                                    ______________________________________                                        T = 70° C.                                                                              36.76 CaCl.sub.2.2H.sub. 2 O/liter DIH.sub.2 O               pH = 8.5         0.4482g Na.sub.2 HPO.sub.4 /liter DIH.sub.2 O                17 hour equilibration                                                         Ca.sup.+2 = 250 ppm as CaCO.sub.3                                             PO.sub.4.sup. -3 = 6 ppm                                                      ______________________________________                                    

Procedure

(1) To about 1800 ml DIH₂ O in a 2 liter volumetric flask, add 20 ml ofCaCl₂ ·2·2H₂ O solution followed by 2 drops of conc. HCl.

(2) Add 40 ml of Na₂ HPO₄ solution.

(3) Bring volume to 2 liters with DI water.

(4) Place 100 ml aliquots of solution in 4 oz glass bottles.

(5) Add treatment.

(6) Adjust pH as desired.

(7) Place in 70° C. water bath and equilibrate for 17 hours.

(8) Remove samples and filter while hot through 0.2 u filters.

(9) Cool to room temperature and take Absorbance measurements usingLeitz photometer (640 nm).

Preparation for Leitz

a. 5 mls filtrate

b. 10 mls Molybdate Reagent

c. 1 dipper Stannous Reagent

d. Swirl 1 minute, pour into Leitz cuvette; wait 1 minute beforereading.

(10) Using current calibration curve (Absorbance vs ppm PO₄ ⁻³) find ppmPO₄ ⁻³ of each sample.

Calculation ##EQU2##

CALCIUM SULFATE INHIBITION PROCEDURE

    ______________________________________                                        CALCIUM SULFATE INHIBITION PROCEDURE                                          Conditions       Chemicals                                                    ______________________________________                                        pH = 7.0         1 × 10.sup.-1 M CaCl.sub.2.2H.sub. 2 O                 T = 50° C.                                                                              1 × 10.sup.-1 M Na.sub.2 SO.sub.4                      24 hour equilibration                                                         Ca.sup.+2 = 2000 ppm                                                          SO.sub.4.sup. -2 = 4800 ppm                                                   ______________________________________                                    

Procedure

(1) Add 50 ml of 10⁻¹ M CaCl₂ ·2H₂ O pre-adjusted to pH 7.0 to a 4 oz.bottle.

(2) Add treatment.

(3) Add 50 ml of 10⁻¹ M Na₂ SO₄ preadjusted to 7.0.

(4) Heat samples for 24 hours in a 50° C. water bath.

(5) Cool for 30 minutes, at least.

(6) Filter 5 ml through 0.45 u filters.

(7) Add NaOH to pH 12.0 and dilute to 50 ml with DI H₂ O.

(8) Add Ca⁺² indicator (1 level).

(9) Titrate to purple-violet endpoint with EDTA.

Calculation: ##EQU3##

CALCIUM PHOSPHONATE PRECIPITATION INHIBITION PROCEDURE

Conditions

Static Beaker Study; 750 ppm Ca⁺² as CaCO₃ ; pH=8.7; T=158° F.; 18 hourEquilibration Time; 10 ppm 1-hydroxyethylidene 1,1-diphosphonic acid(HEDP)

Experimental

Prepare following solutions:

Stock Sol'n-2.206 g CaCl₂ ·2H₂ O+0.033 g HEDP/2 liters.

Treatment-1,000 ppm active solutions.

Procedure

(1) To clean 4 oz bottle add 100 ml of stock solution.

(2) Add treatment with stirring.

(3) Adjust pH to 8.7 with a dilute NaOH sol'n.

(4) Place samples in water bath at T=158° F., for 18 hours, after whichtime filter aliquot through 0.2 u filter paper.

(5) Analyze filtrate for organic phosphate (TP).

Calculation of % Inhibition ##EQU4##

ZINC HYDROXIDE INHIBITION PROCEDURE

Conditions

T=120° F.; Static Beaker Study; Equilibration Time=18 hours; Ca⁺² =170ppm as CaCO₃ ; Mg⁺² =110 ppm as CaCO₃ ; SiO₂ =15 ppm; Zn⁺² =5 ppm;treatment level=5 ppm active.

Solutions

1000 ppm Treatment Solution

Stock Solution

Preparation of Stock Solution

(1) To approximately 9 liters DI water, add 0.5357 g Na₂ SiO₃.5H₂ O.

(2) Adjust pH 6 with concentrated HCl.

(3) Add 2.4996 g CaCl₂ ·2H₂ O.

(4) Add 2.7114 g MgSO₄ ·7H₂ O.

(5) Add 0.1374 g ZnSO₄ ·H₂ O.

(6) Bring volume to 10 liters with DI water.

Procedure

(1) To 800 ml stock solution, add 4 ml treatment solution.

(2) Adjust pH with dilute NaOH.

(3) As each desired pH is reached, place 100 ml of solution in clean 4oz. bottle.

(4) Place in water bath at 120° F. and equilibrate for 18 hours.

(5) Remove samples and filter through 0.2 u filter.

(6) Analyze filtrate for soluble zinc.

(7) Measure and record pH of cooled unfiltered solution.

                  TABLE II                                                        ______________________________________                                        CaCO.sub.3 Precipitation Inhibition                                                        % Inhibition                                                                  Treatment Concentrations (ppm active)                            Treatment      1       3      5     7.5  10                                   ______________________________________                                        Polyacrylic acid                                                                             30.0    63.2   73.7  77.9 78.9                                 MW ≈ 5,000                                                            Acrylic acid/2-hydroxy                                                                       1.7     45.1   56.6  65.3 42.2                                 propylacrylate copolymer                                                      Mn ≈ 2,000                                                            AA/HPA molar ratio                                                            3:1                                                                           Example 1 Copolymer                                                                          0.0     36.4   45.1  56.6 62.4                                 Example 2 Copolymer                                                                          1.7     38.2   50.9  53.8 57.8                                 Example 3 Copolymer                                                                          1.7     30.6   42.2  48.0 45.1                                 Polyacrylic acid                                                                             12.4    71.4   75.7  84.9 86.5                                 MW ≈ 5,000                                                            Example 4 Copolymer                                                                          10.8    56.8   68.6  75.7 75.7                                 Example 5 Copolymer                                                                          8.1     54.1   67.6  73.0 78.4                                 ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Ca.sub.3 (PO.sub.4).sub.2 Precipitation Inhibition                                         % Inhibition                                                                  Treatment Concentrations (ppm active)                            Treatment      5         10        15                                         ______________________________________                                        Acrylic acid/2-hydroxy                                                                       59.3      88.9      90.7                                       propylacrylate copolymer                                                      Mn ≈ 2,000; AA/HPA                                                    Molar ratio 3:1                                                               Sulfonated styrene/                                                                          50.0      81.5      90.7                                       maleic anhydride                                                              copolymer                                                                     MW ≈ 1,500                                                            SS/MA molar                                                                   ratio 3:1                                                                     Example 1 Copolymer                                                                          42.6      90.7      94.4                                       Example 2 Copolymer                                                                          48.1      90.7      100.0                                      Example 3 Copolymer                                                                          53.7      92.6      100.0                                      Acrylic acid/2-hydroxy                                                                       31.7      87.3      87.3                                       propylacrylate copolymer                                                      Mn ≈ 2,000, AA/HPA                                                    molar ratio 3:1                                                               Example 4 Copolymer                                                                          22.2      84.1      93.7                                       Example 5 Copolymer                                                                          12.7      84.1      90.5                                       ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        Calcium Phosphonate Inhibition                                                           % Inhibition                                                                  Treatment Concentration (ppm active)                               Treatment    5        10      15     20                                       ______________________________________                                        Sulfonated styrene/                                                                        2.9      4.4     26.5   72.1                                     maleic anhydride                                                              copolymer                                                                     MW ≈ 1,500                                                            SS/MA molar ratio                                                             3:1                                                                           Example 1 Copolymer                                                                        0.0      0.0     17.6   76.5                                     Example 2 Copolymer                                                                        0.0      0.0     33.8   69.1                                     Example 3 Copolymer                                                                        0.0      2.9     51.5   82.4                                     Sulfonated styrene/                                                                        4.2      5.6     25.4   69.0                                     maleic anhydride                                                              copolymer                                                                     MW ≈ 1,500                                                            SS/MA molar ratio 3:1                                                         Example 4 Copolymer                                                                        0.0      0.0     0.0    2.8                                      Example 5 Copolymer                                                                        0.0      0.0     0.0    0.0                                      ______________________________________                                    

An additional series of acrylic acid/allyl hydroxy propyl sulfonateether (AA/AHPSE) copolymers was prepared according to the methodsearlier described. The polymers were prepared to establish that highermolecular weight copolymers as well as higher molar ratios of theacrylic moiety to the allyl ether in particular AHPSE were effective ininhibiting calcium phosphonate formation and/or deposition in aqueoussystems prone to such. The conclusion drawn by the inventor from thedata is that copolymers of any molar ratios as well as any molecularweight would be effective for the purpose of controlling calciumphosphonate so long as the copolymers would be water soluble, there isan acceptable amount of allyl ether monomer present, and the dosage ofthe copolymer is adequate. The copolymers were subjected to the calciumphosphonate inhibition test earlier detailed. The characteristics of thecopolymers produced as well as the results of this study areincorporated in Tables IVA and IVB which follow: It is noted thatalthough the 6:1 or the 8:1 copolymer was not particularly effective ata 2,000 plus molecular weight (Table I and Table IV) at the dosagestested, the 6:1 copolymers (Table IVB) and most probably the higher8-10:1 are quite effective at the 8-14,000 molecular. As earlier stated,efficacy in many instances is dosage related.

                  TABLE IVA                                                       ______________________________________                                        COPOLYMER PROPERTIES                                                                                       Brookfield                                                                    Vis. cps                                         Copoly-            Mole Ratio                                                                              (25% soln.                                                                            --*                                      mers    Composition                                                                              Monomers  25 C)   Mn                                       ______________________________________                                        A       AA/AHPSE   6/1       21.3     8,000                                   B       AA/AHPSE   6/1       30.5    14,000                                   C       AA/AHPSE   6/1       21.5     8,500                                   D       AA/AHPSE   3/1       12.6     5,500                                   E       AA/AHPSE   3/1       43.5     9,500                                   F       AA/AHPSE   3/1       152.0   >10,000                                  G       AA/AHPSE   3/1       136.6   >10,000                                  H       AA/AHPSE   3/1       94.2    >10,000                                  ______________________________________                                          *Number average molecular weight (Mn) was analyzed by gel permeation         chromatography (GPC) using Toyo Soda G4000 SW column calibrated with          polystyrene sulfonate standard and Shodex OHpak column calibrated with        polyacrylic acid standard. Copolymers F, G and H, due to their high           molecular weights, are outside the limits of resolution of the columns        used. The GPC curves of these three polymers also showed significant          asymmetry which made the calculation of Mn difficult. However, as compare     to Copolymer E which has a Brookfield viscosity of 43.5 cps and Mn of         9,500, the Mn of Copolymers F, G and H are most likely higher than 10,000     since their Brookfield viscosities are much higher than Copolymer E.     

In accordance with Tables IVA and IVB it can be seen that compared toAA/HPA and SS/MA copolymers, copolymers of the invention (CopolymersA-H) are quite effective to inhibit calcium phosphonate. Copolymers A, Band C with a mole ratio of 6/1 and Copolymers F, G and H with numberaverage molecular weight higher than 10,000 are efficacious.

                  TABLE IVB                                                       ______________________________________                                        CALCIUM PHOSPHONATE INHIBITION                                                ______________________________________                                        Conditions:                                                                             750 ppm Ca.sup.2+ as CaCO.sub.3 ; pH 8.7; T = 158 F;                          10 ppm HEDP; 18 hour equilibration time.                                           % Inhibition                                                   Treatment (ppm active)                                                                         5       10      15    20                                     ______________________________________                                        Acrylic acid/hydroxy propyl                                                                    1.1      0.0     0.0   5.7                                   acrylate copolymer                                                            (AA/HPA)                                                                      Sulfonated styrene/maleic                                                                      0.0      3.4    53.4  83.4                                   anhydride copolymer                                                           (SS/MA)                                                                       Copolymer A      0.0      0.0    39.8  79.5                                   Copolymer B      0.0      5.2    32.8  70.9                                   Copolymer C      0.0     21.6    86.4  76.1                                   Copolymer D      0.0     85.2    100.0 100.0                                  Copolymer E      0.0     92.0    98.9  65.9                                   Copolymer F      0.0     94.3    100.0 93.1                                   Copolymer G      0.0     75.0    88.6  80.7                                   Copolymer H      5.7     84.1    98.9  94.3                                   ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        Zinc Hydroxide Inhibition                                                                                 ppm Soluble                                                                   Zinc after 18                                     Treatment        Final pH   Hours                                             ______________________________________                                         No treatment    7.42       3.3                                                                7.60       1.5                                                                8.10       0.3                                                                8.47       0.1                                                                8.79       0.1                                                                9.09       0.1                                               Acrylic acid/2-hydroxy                                                                         7.12       4.3                                               propylacrylate copolymer                                                                       7.55       3.8                                               Mn ≈  2,000; AA/HPA                                                                    7.93       3.7                                               molar ratio 3:1  8.15       3.8                                                                8.64       3.8                                                                9.04       3.6                                               Sulfonated styrene/                                                                            7.40       4.0                                               maleic anhydride 7.68       3.8                                               copolymer MW ≈ 1,500                                                                   8.06       3.9                                               SS/MA molar ratio                                                                              8.35       4.2                                               3:1              8.77       4.0                                                                9.08       3.5                                               Example 1 Copolymer                                                                            7.03       4.3                                                                7.62       4.6                                                                7.96       4.6                                                                8.29       4.2                                                                8.64       4.2                                                                8.96       4.0                                               Example 2 Copolymer                                                                            7.12       4.2                                                                7.64       4.6                                                                7.90       4.0                                                                8.29       4.5                                                                8.57       4.0                                                                9.10       3.7                                               Example 3 Copolymer                                                                            7.20       4.2                                                                7.64       4.6                                                                7.94       4.6                                                                8.33       4.3                                                                8.67       4.4                                                                9.06       4.2                                               No Treatment     7.27       3.5                                                                7.63       1.6                                                                8.03       0.3                                                                8.48       0.1                                                                8.73       0.1                                                                9.05       0.1                                               Example 4 Copolymer                                                                            7.22       3.7                                                                7.65       3.8                                                                8.02       3.7                                                                8.43       3.4                                                                8.73       4.1                                                                9.05       4.1                                               Example 5 Copolymer                                                                            7.24       3.8                                                                7.60       3.3                                                                8.01       3.6                                                                8.37       3.9                                                                8.72       3.5                                                                9.03       4.1                                               ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                        Ca.sub.3 (PO.sub.4).sub.2 Precipitation Inhibition                                          % Inhibition                                                                  Treatment Concentration (ppm active)                            Treatment     10 ppm                                                          ______________________________________                                        Acrylic       70.4                                                            acid/2-hydroxy                                                                propylacrylate                                                                Mn ≈  2,000; AA/HPA                                                   molar ratio 3:1                                                               Example 1 Copolymer                                                                         90.7                                                            Example 2 Copolymer                                                                         94.4                                                            Example 3 Copolymer                                                                         94.4                                                            ______________________________________                                    

                  TABLE VIa                                                       ______________________________________                                        Ca.sub.3 (PO.sub.4).sub.2 Precipitation Inhibition                                           Treatment                                                      Treatment      Level (ppm)  % Inhibition                                      ______________________________________                                        Example 1 Copolymer                                                                           2.5         25.9                                              Example 1 Copolymer                                                                           5.0         46.3                                                             10.0         90.7                                                             20.0         100.0                                             Example 2 Copolymer                                                                           2.5         18.5                                                              5.0         44.4                                                             10.0         94.4                                                             20.0         100.0                                             Example 3 Copolymer                                                                           2.5         38.9                                                              5.0         42.6                                                             10.0         94.4                                                             20.0         100.0                                             Acrylic acid/   2.5         31.5                                              2-hydroxypropyl                                                                               5.0         44.4                                              acrylate copolymer                                                                           10.0         70.4                                              Mn ≈ 2,000; AA:HPA                                                                   20.0         98.1                                              molar ratio = 3:1                                                             ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                        Calcium Carbonate Precipitation Inhibition                                                   Treatment                                                      Treatment      Level (ppm)  % Inhibition                                      ______________________________________                                        Example 1 Copolymer                                                                          0.5          25.0                                                             1.0          53.6                                                             3.0          70.3                                                             5.0          74.5                                              Example 2 Copolymer                                                                          0.5          27.1                                                             1.0          55.7                                                             3.0          63.0                                                             5.0          71.4                                              Example 3 Copolymer                                                                          0.5          26.6                                                             1.0          47.9                                                             3.0          66.7                                                             5.0          65.6                                              Polyacrylic acid                                                                             1.0          31.0                                              MW ≈ 5,000                                                                           3.0          61.0                                                             5.0          59.7                                                             10.0         66.7                                              ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                        Calcium Sulfate Inhibition                                                                   Treatment                                                      Treatment      Level (ppm)  % Inhibition                                      ______________________________________                                        Example 1 Copolymer                                                                          0.5          10.4                                                             1.0          24.3                                                             3.0          88.4                                                             5.0          98.6                                              Example 2 Copolymer                                                                          0.5           8.1                                                             1.0          18.9                                                             3.0          97.3                                                             5.0          97.5                                              Example 3 Copolymer                                                                          0.5          7.5                                                              1.0          16.5                                                             3.0          92.9                                                             5.0          97.2                                              Polyacrylic acid                                                                             1.0          97.0                                              MW ≈ 5,000                                                                           3.0          98.0                                                             5.0          98.0                                              ______________________________________                                    

Ferric Oxide Dispersion

In order to demonstrate the effectiveness of the polymers of theinvention in dispersing suspended particulate matter, the followingprocedure, using Fe₂ O₃ as suspended solids, was undertaken. Resultsappear in Table IX. In the results, it is noted that increasing Δ%Tvalues indicate better treatment as more particles remain suspended inthe aqueous medium.

Fe₂ O₃ Dispersion Procedure

    ______________________________________                                        Fe.sub.2 O.sub.3 Dispersion Procedure                                         Conditions:    Solutions:                                                     ______________________________________                                        T = 25° C.                                                                            0.1% solution Fe.sub.2 O.sub.3 in D.I. H.sub.2 O               pH = 7.5       3.68 g CaCl.sub.2.2H.sub. 2 O/100 ml DI H.sub.2 O              200 ppm Ca.sup.+2 as CaCO.sub.3                                               ______________________________________                                    

Procedure

(1) Prepare a suspension of 0.1% Fe₂ O₃ in DI H₂ O.

(2) Adjust hardness to 200 ppm Ca⁺² as CaCO₃ using CaCl₂ ·2H₂ Osolution-8 ml/1000 ml of Fe₂ O₃ solution.

(3) Using overhead mixer, mix suspension 1/2 hour at 1000 rpms.

(4) Remove solution to magnetic stirrer and adjust to pH 7.5 (about 20minutes to stabilize pH).

(5) Return solution to overhead mixer.

(6) Take 90 ml aliquots of suspension and place 4 oz. glass bottle.

(7) Add treatment and DI water to bring total volume to 100 ml.

(8) Cap bottle, invert several times and place on reciprocating shakerat a moderate speed of about 40 spm for 1/2 hour.

(9) Place on vibration-proof surface and allow to stand 18 hours.

(10) Without disturbing settled phase, pipet the top 40 mls off thesample. Place in a cell and read %T (at 415 nm).

Calculation:

Δ%T=%T (control)-%T (treated)

                  TABLE IX                                                        ______________________________________                                                           Treatment                                                  Treatment          Level (ppm)                                                                              Δ % T                                     ______________________________________                                        Example 1 Copolymer                                                                               2.5        7.5                                                                5.0       20.7                                                               10.0       21.2                                                               20.0       20.7                                            Example 2 Copolymer                                                                               2.5       12.0                                                                5.0       10.0                                                               10.0       10.2                                                               20.0       10.7                                            Example 3 Copolymer                                                                               2.5       15.1                                                                5.0       23.1                                                               10.0       25.9                                                               20.0       25.4                                            Acrylic acid/2-hydroxy                                                                            2.5       9.3                                             propyl acrylate Mn ≈ 2,000                                                                5.0       15.4                                            molar ratio AA.HPA = 3:1                                                                         10.0       15.1                                                               20.0       16.4                                                               30.0       16.9                                            ______________________________________                                    

Recirculator Studies

In order to approximate those conditions experienced in a cooling tower,tests were conducted under recirculatory conditions with heat transferprovided.

These conditions closely simulate the environment in a field coolingsystem. In this test system treated water is circulated by a centrifugalpump through a corrosion coupon by-pass into which corrosion coupons areinserted, and past a mild steel (AISI-1010) heat exchanger tubecontained in a plexiglass block. The inside of the exchanger tube isfilled with silicone oil and heated with an electric heater. Thetemperature of the silicone oil can be regulated. The water velocitypast the corrosion coupons and heat exchanger tube can be controlledanywhere from 0 to 4.5 ft/sec.

The pH and temperature of the bulk water are automatically controlled.The treated water is prepared by chemical addition to deionized water.Provisions for continuous make-up and blowdown are made by pumping freshtreated water from supply tanks to the sump, with overflow from the sumpserving as blowdown.

Corrosion rates are determined by exposing precleaned and weighed metalspecimens for a specified period of time, after which they are removed,cleaned and reweighed. Corrosion rates are calculated by dividing thetotal coupon weight loss by the number of days of exposure.

The conditions used were: Heat Flux 8000 BTU/ft² /hr; Water Velocity=3ft/sec; Water Temperature=120° F.; Retention Time=1.3 days; Mild SteelHeat Transfer Surface.

Water Chemistry: 600 ppm Ca as CaCO₃ ; 300 ppm Mg⁺² as CaCO₃ ; 83 ppmNaHCO₃ ; pH=7.3±0.2.

Treatment: 12.5 ppm active polymer; 3.0 ppm tolyltriazole; 10.5 ppmtetrapotassium pyrophosphate; 15.2 ppm monosodium phosphate; HEDP 4.0ppm.

The following results were obtained:

                  TABLE X                                                         ______________________________________                                                          Pretreated                                                          Mild Steel                                                                              Mild Steel                                                                              Admiralty                                         Treatment                                                                             Corrosion Corrosion Corrosion                                                                             Remarks                                   ______________________________________                                        Example 1                                                                             1.2 mpy   0.1 mpy   0.1 mpy No significant                            Copolymer                           corrosion or                                                                  deposition on                                                                 steel sur-                                                                    faces.                                    Example 2                                                                             1.2 mpy   0.9 mpy   0.5 mpy No significant                            Copolymer                           corrosion or                                                                  deposition on                                                                 mild steel                                                                    surfaces.                                 Example 3                                                                             1.1 mpy   0.8 mpy   0.5 mpy No significant                            Copolymer                           corrosion or                                                                  deposition on                                                                 mild steel                                                                    surfaces.                                 ______________________________________                                    

Example 8 Copolymer of Methacrylic Acid and AHPSE

Utilizing both apparatus and procedure similar to that described inExample 1, 228 g. of water and 180 g of AHPSE (40% solution, 0.33 mole)were added to a reaction flask, 86 g. of methacrylic acid (1 mole) andsodium persulfate solution were then separately added to the reactionmixture over a two hour period at 85° C. The resulting polymer solutionwas further neutralized with 70 g of caustic (50%) and diluted to a 25%solids solution. The final solution had a Brookfield viscosity of 28.2cps at 25° C. The molecular weight Mn of the copolymer was 3,400.

Boiler Studies

In order to assess the efficacy of the polymers of the present inventionin inhibiting scale formation in steam generating systems, researchboilers were fitted with two 4,000 watt electrical heater probes, giving185,000 BTU/ft² /hr and about 8 Kg/hr steam. The boiler feedwatercontained the contaminants and treatment agents given hereinbelow. Theboilers were operated for 44 hours per run at an average of 15 cycles ofconcentration. At the conclusion of each run, the deposts were cleanedfrom the probes with an acid solution and the deposit densities werethen calculated.

Boiler Test Conditions

Condition "A"

sodium sulfide oxygen scavenger, 900 psig, contaminants 4/1/1 ppmCa/Mg/Fe in feedwater, stoichiometric amount of EDTAadded--chelant/polymer program.

Condition "B"

sodium sulfite oxygen scavenger, 900 psig, contaminants 4/1 ppm Ca/Mg infeedwater, phosphate added to produce 30 ppm PO₄ as Ca--phosphateprecipitation/polymer program.

Condition "C"

hydrazine oxygen scavenger, 1450 psig, contaminant 5 ppm Fe infeedwater, phosphate added to produce 7 ppm PO₄ as Ca--coordinatedphosphate/pH/polymer.

The results appear hereinbelow in Table XI.

                  TABLE XI                                                        ______________________________________                                                              Treatment Dosage                                                                            Average                                   Condi-                ppm polymer   Deposit                                   tion  Polymer         (actives)     (g/ft.sup.2)                              ______________________________________                                        A     Polymethacrylic acid                                                                          5             0.18                                            Mw 12,000 (sodium salt)                                                 A     Example 8       5             0.19                                            Copolymer                                                               B     Sulfonated Polystyrene                                                                        7.5           0.23                                            Maleic Anhydride                                                              Copolymer MW                                                                  3,000-5,000 SSMA                                                              (3:1)                                                                   B     Example 8       7.5           0.23                                            Copolymer                                                               C     Polymethacrylic acid                                                                          5             0.93                                            Mw 12,000 (Sodium Salt)                                                 C     Example 8       5             2.55                                            Copolymer                                                               ______________________________________                                    

Discussion

The examples demonstrate that the copolymers of the present inventionare effective in inhibiting the formation of those deposits normallyencountered in industrial water systems such as cooling and boilersystems. Further, the copolymers are effective in dispersing iron oxidewhich is sometimes encountered as a troublesome fouling species.

The demonstrated efficacy of the copolymers in inhibiting calciumphosphate, and calcium phosphonate precipitation is very important. Forinstance, one successfully established cooling water treatment methodprovides a passivated oxide film on metal surfaces in contact with theaqueous medium via addition of orthophosphate, organo-phosphonate and anacrylic acid/hydroxylated alkyl acrylate copolymer. Details of suchmethod are disclosed in U.S. Pat. No. 4,303,568 (May et al.). The entirecontent of this patent is hereby incorporated by reference. Based uponthe deposit control efficacy shown by the instant copolymers, as well asthe minimum corrosion rates displayed herein in the recirculatorstudies, it is thought that the subject copolymers can be substitutedfor the polymers disclosed in the aforementioned May et al. patent so asto provide the important passivated oxide film on the desired metalsurfaces.

As the copolymers are effective in inhibiting calcium phosphateformation, they would also be effective in gas scrubbing systems wherescrubbing mediums such as sewage treatment effluents contain highphosphate levels. Such systems would have the prerequisite for theformation and deposition of calcium phosphate which is to be avoided.Additional areas of application such as the phosphate production andprocessing field, fertilizer field, automotive metallic partpretreatment field, etc. will be apparent to those skilled in the art.

The fact that the instant copolymers provide for increased soluble zincconcentrations in solution (Table V) is important in that more zinc isleft in the system water so as to provide its well known corrosionprotection. Without the use of the copolymers of the present invention,more zinc precipitates in the form of zinc hydroxide, thus leaving lesszinc available for its all important anti-corrosion protection. As such,it is postulated that the present copolymers can be successfullyemployed in zinc-based corrosion protection systems such as thosedisclosed in U.S. Pat. No. 3,510,436 (Silverstein), the content of whichis hereby incorporated by reference.

The boiler studies demonstrate that a polymethacrylic acid/AHPSEcopolymer in accordance with the invention is comparable to thewell-known polymethacrylic acid and polysulfonated styrene/maleicanhydride polymeric treatments in inhibiting deposits in boilers.Accordingly, the polymethacrylic acid/AHPSE copolymer of Example 8 ispreferred for use in boiler environments.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. A method of controlling the deposition of calcium phosphateon the structural parts of a system exposed to an aqueous mediumcontaining said calcium and phosphate ions under deposit formingconditions, said method comprising adding to said aqueous medium aneffective amount for the purpose of a water soluble polymer comprisingrepeat unit moieties (a) and (b) wherein said repeat unit (a) comprisesthe structure ##STR10## and wherein said repeat unit (b) comprises thestructure ##STR11## wherein each R₁ is independently H or lower alkyl(C₁ -C₃); R₂ is OH or OM; M is a water soluble cation; R₃ is2,hydroxypropylidene; and Z is H or a water soluble cation or cationswhich together counterbalance the valence of SO₃ ; and said polymer hasa molar ratio x:y of about 4:1 to 3:1 and a number average molecularweight of about 1,500 to 14,000, or said polymer has a molar ratio x:yof about 6:1 and a molecular weight of about 8,000 to 14,000.
 2. Amethod as recited in claim 3, wherein R₁ in both said repeat units (a)and (b) is hydrogen, R₂ is OH and Z is a member or members selected fromthe group consisting of H, Na, NH₄ ⁺, Ca and K.
 3. A method as recitedin claim 2, wherein said water soluble polymer is added to said aqueousmedium in an amount of 0.1-500 parts polymer based upon 1 million partsof said aqueous medium.
 4. A method as recited in claim 3, wherein saidsystem is a steam generating system.
 5. A method as recited in claim 3,wherein said system is a cooling water system.
 6. A method as recited inclaim 3, wherein said system is a gas scrubbing system.